1. Field of the Invention
This invention relates to a novel method of separating colloidal particles from an aqueous solution, and particularly relates to separating fine zeolite crystals from their mother liquor.
2. Description of the Prior Art
Crystalline aluminosilicate zeolites, such as ZSM-5 and ZSM-35, may be prepared from an aqueous mother liquor solution containing sources of alkali metal oxide, aluminum oxide, silicon oxide, and ethylenediamine, pyrrolidine or tetrapropylammonium cations (U.S. Pat. No. 3,702,886 and 4,016,245). The crystals produced are generally in the size range of 0.005 to 0.3 micron in diameter and remain suspended or dispersed in the mother liquor in a colloidal state (U.S. Pat. Nos. 3,992,466 and 3,926,782). Since ordinary filters have paper or canvas filter cloths with pore sizes of approximately 40 microns, such filters are impractical for use in separating the zeolite particles from the mother liquor.
In attempting to solve the problem of separating the dispersed zeolites from the solution, the prior art has suggested the use of various agglomerating agents, centrifuges, flocculants and frothing systems (U.S. Pat. No. 3,902,993). A simple, yet highly effective method has now been developed which is quite suitable for laboratory or commercial processes and has the added advantage in that the method does not require the use of costly additional equipment.